Si Surface Barrier Detector Research Articles

A liquid-scintillation-based primary standardization of 210Pb

A new radioactivity solution standard of 210Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new 210Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L −1 nitric acid solution, has a density of (1.028±0.002) g mL −1 at 20 °C, has carrier ion concentrations of about 11 μg Pb 2+ and 21 μg Bi 3+ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g −1 as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the 210Pb content of the solution was based on 4 παβ liquid scintillation (LS) measurements using CIEMAT/NIST 3H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2 πα spectrometry with a Si surface barrier detector of separated 210Po, and by 4 πβ(LS)– γ(NaI) anticoincidence counting.

Progress and application of the Tohoku microbeam system

A microbeam system was constructed at the Tohoku University Dynamitron laboratory and optimization of the system was performed. Parasitic field contamination from tungsten carbide slit chips and an annular Si surface barrier detector limited the beam spot size to 2 × 2 μm 2. By replacing these components, the parasitic field contamination of the system was reduced and the performance of the microbeam system was remarkably improved. A measured beam spot size of 0.4 × 0.4 μm 2 at a beam current of several tens of pA has been accomplished. The results obtained using the grid shadow method show that a beam spot size of less than 0.4 μm is obtainable in the low-current regime. For easy tuning and operation of the microbeam system, a human–machine interface (HMI) was developed based on the user participatory design concept. The HMI has been accepted favorably by users and is used in routine operations. The analysis system has been re-developed and is applicable to simultaneous in-air/in-vacuum PIXE, RBS, SEM, and STIM analyses and 3D μ-CT. The system is now applied for studies in biological, environmental, and other fields.

Application of pulse shape discrimination in Si detector for fission fragment angular distribution measurements

Pulse shape discrimination (PSD) with totally depleted transmission type Si surface barrier detector in reverse mount has been investigated to identify fission fragments in the presence of elastic background in heavy ion-induced fission reactions by both numerical simulation and experimental studies. The PSD method is compared with the other conventional methods adopted to identify fission fragments with solid-state detectors such as ΔE–E telescope and single thin ΔE detector and the data for the10B +232Th fission reaction are presented. Results demonstrate the usefulness of a single transmission-type surface barrier detector for the identification of fission fragments and projectiles like heavy ions

Analysis of nanolayered samples with a 4He beam

We analysed Si(100)/Al2O3 500nm/(CoFeB 2–7nm/Al2O3 0.7–1.5nm)×4/Ta 2nm multilayers. Layer thickness, composition and roughness, as well as interdiffusion on annealing, are important parameters to be determined. This poses an extreme challenge to any analysis technique. We show that the technique of choice can be Rutherford backscattering with an inexpensive Si surface barrier detector, complemented by elastic recoil detection analysis and X-ray diffraction experiments.

P−sdShell Gap Reduction in Neutron-Rich Systems and Cross-Shell Excitations inO20

Excited states in 20O were populated in the reaction 10Be(14C,alpha) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and gamma radiation was detected with the FSU gamma detector array. Five new states were observed below 6 MeV from the alpha-gamma and alpha-gamma-gamma coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added.

Detection of single and resonant projectile fragments in 12C-induced reactions to the continuum

Detector telescopes having a Δ E – E configuration, consisting of either a Si surface barrier detector or a Si strip detector followed by a NaI(Tl) stopping detector, are described for measuring intermediate mass fragments in 12C-induced reactions to the continuum. These include the stable break-up fragments 7Be and 9Be, as well as the resonant fragment 8Be. Energy calibration of the stopping detectors is based on a scintillation light-response model. Empirical approximating functions have been selected for inverting the theoretical functions relating light output to particle energy, in order to achieve calibration during rapid data sorting. The detector efficiency for resonant fragments is obtained by means of a Monte Carlo simulation. A dedicated eight-channel preamplifier module with good operational stability in vacuum, specifically designed for Si-strip detectors, is also described.

Implantation sites of Ce and Gd in diamond

The implantation sites of rare earth (RE) probes 141 Ce ( t 1/2=32 d) and 149 Gd ( t 1/2=9.28 d) in diamond have been investigated using the emission channeling (EC) technique. Parent isotopes 141 Cs and 149 Dy were implanted into type IIa diamond samples at an energy of 60 keV at the online isotope separator ISOLDE at CERN. 141 Cs decays through the chain 141 Cs– 141 Ba– 141 La– 141 Ce– 141 Pr. EC measurements were made on the 102 keV conversion electrons emitted in the decay of 141 Pr to its ground state. The decay of 149 Dy follows the chain 149 Dy– 149 Tb– 149 Gd– 149 Eu– 149Sm. EC measurements were made on the 101 keV electrons emitted in the decay of 149 Eu. Two-dimensional channeling patterns of the conversion electrons were obtained along 〈1 1 0〉 and 〈1 1 1〉 axial directions by raster scans with a Si surface barrier detector. Comparison of the observed patterns with simulated spectra show that in diamond 45–50% of the RE atoms are located near substitutional sites, unlike the case in Si.

Preparation of Thick Americium Targets and Synthesis of 259Db

A new isotope of Db has been produced via the reaction Am(Ne, 4n) at Elab = 118 MeV, and its half-life of 0.51± 0.16 s and α-decay energy of 9.47 MeV were determined in this work. The americium targets with thickness ranged from 0.7 to 1.0 mg/cm were prepared by molecular plating method through a single electrodeposition cycle. The reaction products were transported and collected using a helium-jet technique and a rotating wheel apparatus. The α decays of both the products and their daughter nuclides were detected by a series of Si(Au) surface barrier detectors arranged ingeniously. The identification of Db was performed based on the genetic relationship between the new activity and the known Lr established by α-recoiled milking measurement. The Qα value of Db derived from the present experiment is in good agreement with theoretical prediction.

Fission fragment mass reconstruction from Si surface barrier detector measurement

A method for plasma delay and pulse-height defect corrections for Si surface barrier detectors (SBD) is presented. Based on known empirical formulae, simple approximations involving the measured time of flight (TOF) and energy of the ions were found and a mass reconstruction procedure was developed. The procedure was applied for obtaining the fission fragment mass and angular distributions from the 64Ni+ 197Au reaction at 418 and 383 MeV incident energy using an array of eight SBDs.

Pulse time interval analysis (TIA) combined with liquid scintillation counting for the determination of environmental α-nuclides: Preparation and utilization of225Ra as a yield tracer

Time interval analysis (TIA), which has been verified to be suitable for the selective extraction of correlated successive α-decay events within a liquid scintillator, was further developed by combining pulse shape discrimination technique and simple chemical analysis. A β-emitter nuclide,225Ra, which is suitable for the use as a yield tracer belonging to Np-decay series, was also found to be detectable by the TIA-method after a certain standing period when the radium-extractant (RADAEX) was added small amounts of HDEHP [di (2-ethylhexyl) phosphoric acid], which was proved to keep the equilibrium state between Ra and its descendants. The present counting system (TIA analysis incorporated α-LSC/PSD) has been verified to be applicable to the simultaneous determination of three (including Th, Ac, and Np) decay series, if the chemical purification of radium fraction was applied to the environmental samples using an extractive scintillator in addition to utilization of an α-peak itself at lowest energy for the determination of226Ra in uranium decay series. This radioanalytical method was practically applied to the determination of natural radionuclides belonging to three decay series in environmental samples and compared to the alpha-spectrometric results using a Si-surface barrier detector (SSB).

Convoy Electron Production and Ionization in 390 MeV/u Ar17+ Ion Collisions with Thin Foils

Interactions of relativistic clothed heavy ions with solid targets have been studied for 390 MeV/u Ar17+ ions traversing carbon foils of various thicknesses through measurements of the convoy electrons. The electron energy spectra at 0° were obtained by a magnetic analyzer combined with a Si surface barrier detector with a depletion layer of 5 mm. The peak widths of the convoy electrons in the laboratory frame have been found to decrease as the target thickness is increased from 25 to about 500 µg/cm2, and broaden for thicker targets due to multiple scattering.

Resonant coherent excitation of 390 MeV/u Ar ions planar channeled in Si crystals

Resonant coherent excitation of the 1s electron to n=2 states in a hydrogen-like ion was studied through measurements of the survived fraction of 390 MeV/u Ar17+ planar channeled in a Si crystal. Adopting a totally depleted Si surface barrier detector as a target crystal, the charge state of the individual emerged ion was measured in coincidence with the energy deposition in the target. By changing the incident direction along the (220), (004), and (111) planes, a series of clear resonances were observed as the decrease in the survived charge fraction due to higher electron loss probability for the excited state. Each resonance profile reflects energy splitting of the n=2 manifold originated from l–s interaction and Stark effect due to the crystal field. From the correlation between the energy loss and survived charge fraction, transition energy as a function of the ion trajectory amplitude is deduced which is in good agreement with calculated results.

Electron-γ angular correlations in134Ba

Electron-\ensuremath{\gamma} directional correlation measurements have been done in ${}^{134}\mathrm{Ba}$ for the first time using an apparatus including cooled Si surface barrier detector for the electrons and HPGe for the \ensuremath{\gamma}'s. Experimental particle parameters for pure intense E2 transitions have been calculated from \ensuremath{\gamma}\ensuremath{\gamma} and electron-\ensuremath{\gamma} results, giving ${b}_{2}(605K)=1.31(28)$ and ${b}_{2}(795K)=1.20(23).$ Some mixed transitions were also analyzed. The $326K$ electron conversion ratio ${\ensuremath{\alpha}}_{326K}=14(6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ was measured. An upper bound for the E0/E2 mixing ratio was estimated to the ${2}^{+\ensuremath{'}}\ensuremath{\rightarrow}{2}^{+}(563$ keV) transition by the $e\ensuremath{\gamma}$ interference E0/E2 method, giving ${q}_{K}^{2}(E0/E2)l~0.06.$

New data on alpha-particle emission probabilities of several actinide nuclides

New data on alpha-particle emission probabilities in the decays of 233U, 238Pu, 244Cm, 242Cm, 243Am, and 241Am have been determined by using Au–Si surface barrier detectors and the multiplet alpha-spectra analysis program MULT. The sources were prepared by electrodeposition method, and the energy resolution (fwhm) amounted to 15–16 keV. The total uncertainties of the strongest line of each nuclide except 233U are about 0.1%. Our results are compared to those obtained by using magnetic spectrographs and semiconductor detectors.

An external milli-beam for archaeometric applications on the AGLAE IBA facility of the Louvre museum

External beam lines have been built on numerous IBA facilities for the analysis of works of art to avoid sampling and vacuum potentially detrimental to the integrity of such precious objects. On the other hand, growing interest lies on microprobe systems which provide a high lateral resolution but which usually work under vacuum. Until recently, the AGLAE facility was equipped with separate external beam and microprobe lines. The need of a better spatial resolution in the external beam mode has led us to combine them into a single system which exhibits numerous advantages and allows the analysis of small heterogeneities like inclusions in gemstones or tiny components of composite samples. The triplet of quadrupole lenses bought from Oxford is used to focus the beam. By using a 0.75 μm thick Al foil as the exit window, blowing a helium flow around the beam spot and reducing the window-sample distance below 3 mm, a beam size of about 30 μm can be reached. The experimental setup includes two Si(Li), a HPGe and a Si surface barrier detectors for the simultaneous implementation of PIXE, NRA and RBS. The full description of this device is given as well as a few applications to highlight its capability.

Resonant coherent excitation of relativistic Ar 17+ ions channeled in a Si crystal

We observed resonant coherent excitation (RCE) of 1s electron to n=2 states in Ar 17+ through measurements of the survived fraction of 390 MeV/u hydrogen-like Ar 17+ channeled in a Si crystal. We adopted a totally depleted Si surface barrier detector as a target crystal as well as a probe of the energy deposition. The charge state of emerged ions was measured by a combination of a charge separation magnet and a 2D-position sensitive detector. We observed the RCE for planar channeled ions by tilting the target Si crystal from the direction of [1 1 0] axis in the (2 2 ̄ 0) , (0 0 4) , and (1 1 ̄ 1) planes. Prominent resonances at tilt angles under the resonance condition were observed. Moreover, each resonance profile is split into several lines due to the l· s interaction and the Stark effect originating in the static crystal field. The energy deposition in the crystal gives the information of the amplitude of the ion trajectory. The resonance peak position, intensity and width in the survived fraction of Ar 17+ reflect the position dependent strength of the crystal field, the RCE and the electron loss probabilities. They are in good accord with our calculation of the transition energy and probability.

Determination of the volume activity concentration of alpha artificial radionuclides with alpha spectrometer.

This paper introduces a method to determine the volume activity concentration of alpha and/or beta artificial radionuclides in the environment and radon/thoron progeny background-compensation based on a Si surface-barrier detector. By measuring the alpha peak counts of 218Po and 214Po in two time intervals, the activity concentration of 218Po, 214Pb and 214Bi aerosol particles were determined; meanwhile, the total beta count of 214Pb and 214Bi aerosols was also calculated from their decay scheme. With the average equilibrium factor of thoron progeny in general environment, the alpha and beta counts of thoron progeny were approximately evaluated by 212Po alpha peak counts. The alpha count of transuranic aerosols was determined by subtracting the trail counts of radon/thoron progeny alpha peaks. The total count of beta artificial radionuclides was determined by subtracting the beta counts of radon/thoron progeny aerosol particles. In our preliminary experiments, if the radon progeny concentration is less than 15 Bq m(-3), the lower limit of detection of transuranics concentration is less than 0.1 Bq m(-3). Even if the radon progeny concentration is as high as 75 Bq m(-3), the lower limit of detection of total beta activity concentration of artificial nuclides aerosols is less than 1 Bq m(-3).

96/03277 - 10-MW demonstration of the AirPol Gas Suspension Absorption flue gas desulfurization process

New data on alpha-particle emission probabilities in the decays of 233U, 238Pu, 244Cm, 242Cm, 243Am, and 241Am have been determined by using Au–Si surface barrier detectors and the multiplet alpha-spectra analysis program MULT. The sources were prepared by electrodeposition method, and the energy resolution (fwhm) amounted to 15–16 keV. The total uncertainties of the strongest line of each nuclide except 233U are about 0.1%. Our results are compared to those obtained by using magnetic spectrographs and semiconductor detectors.

Analysis technique of multiplet alpha spectra

Two line shape functions have been chosen to accurately represent the form of monoenergetic peaks in alpha spectra measured with Si surface barrier detectors. A method to evaluate line shape parameters by means of doublet alpha spectra is introduced. Nonlinear parameters are calculated with Marquardt's method. A program MULT has been written to analyze multiplets in alpha spectra, and has been tested using a synthetic spectrum. The program MULT has been used to calculate alpha-particle emission probabilities in the decay of 241Am and 244Cm, and the 240Pu/ 239Pu alpha activity ratio in plutonium samples.

Study of charged particles emitted in the β-decay of 6,8He

The beta-delayed charged particle spectra from 6He and 8He were measured with a telescope consisting of a gas counter and a Si surface barrier detector. Beta-delayed deuterons and tritons are emitted in the two cases with branching ratios of (7.6±0.6) × 10 −6, E d > 350 keV and (8.0±0.5) × 10 −3, respectively. Both spectra present anomalies that must be due to the special structure of these nuclei (an alpha core surrounded by several neutrons).